The movements involved in flight of some missiles and space vehicles, such as pitch, yaw, and spin rate, are controlled with flight control systems that use reaction jets. In some systems of this type, a pressurized gas source, such as a gas generator, supplies a pressurized gas to one or more fluidic amplifier stages. In response to a control signal supplied from flight control equipment, a fluidic amplifier stage can selectively divert the pressurized gas into one of two or more flow paths. Each flow path may have a nozzle on its outlet that is located external to the missile or vehicle. These nozzles may be positioned to provide thrust in different or opposite directions. Thus, the fluidic amplifier stages can affect one or more flight parameters by selectively diverting the pressurized gas to selected outlet nozzles.
The fluidic amplifier stages incorporated into the above-described flight control system can include non-vented fluidic amplifiers, which are generally known in the art. However, non-vented fluidic amplifiers may not provide 100% flow diversion. Thus, some systems incorporate an additional element, such as a diverter valve, between the final fluidic amplifier stage and the output nozzles, which allows the system to substantially achieve 100% flow diversion.
One particular type of diverter valve includes a valve element that located in a valve bore formed in the valve housing. The housing includes an inlet port and two outlet ports. The housing additionally includes two valve seats that each surrounds one of the two outlet ports. The valve element is moveable within the valve bore, and selectively seats against one of the two valve seats, and thereby blocks one of the two ports so that pressurized gas entering the inlet port is selectively directed out the port that is not blocked. For high-temperature applications, such as those that may be encountered in missile and spacecraft propulsion systems, refractory metals, such as rhenium, and carbon-based materials, such as graphite, may be used to construct the valve element. In some cases, rhenium coated graphite valve elements are used.
Although the above-described type of diverter valve is robustly designed and manufactured, and operates safely, it suffers certain drawbacks. For example, to provide the desired switching performance of the valve element, a relatively small valve-element-to-seat contact area is included in the valve. However, the relatively small contact area can, in many instances, result in the valve element experiencing an impact load during operation that is concentrated on a relatively small area of the valve element. This concentrated impact load can damage the valve element, which can adversely impact system performance, shorten valve element lifetime, and/or reduce overall system reliability.
Hence, there is a need for a diverter valve that addresses one or more of the above-noted drawbacks. Namely, a hot gas diverter valve having a valve element that experiences reduced impact loading during operation, and thus does not adversely impact system performance, and/or does not shorten valve element lifetime, and/or enhances overall system reliability. The present invention addresses one or more of these needs.